Under normal nutritional and physiological conditions, fuel requirements of the body are met primarily by glucose and fatty acid metabolism. However, during abnormal metabolic stress states induced by trauma or sepsis, one of the effects is a decrease of fat and glucose utilization. Under these conditions, a high rate of bodily protein catabolism occurs. This metabolic response results in the acceleration of protein degradation and an elevation of energy expenditure, or hypercatabolism. Bodily protein catabolism provides the precursors for oxidation of branched chain amino acids and the synthesis and release of alanine for hepatic metabolism as a gluconeogenic substrate. Urinary nitrogen excretion is often elevated and the individual suffers a negative nitrogen balance. If the stress is persistent, the nitrogen losses will eventually deplete the individual's protein stores resulting in a progressive deterioration of lean body mass and multiple organ failure.
Stress of injury in an individual, such as trauma or sepsis, is often accompanied by total or partial dysfunction of the gastro-intestinal tract. These individuals are often hospitalized and must receive most or all of their daily nutritional requirements parenterally and/or enterally in order to sustain protein synthesis and avoid malnutrition. For example, many patients are administered total parenteral nutrition which includes a source of fatty acids. Standard parenteral nutrition diets have long chain fatty acid triglyceride (LCT) emulsions, composed of either soybean or safflower oil, as the primary lipid source. These oils are high in .omega.6 fatty acids, particularly linoleic acid.
As an alternative or additive fatty acid source, medium chain triglycerides (MCT) formed from saturated fatty acids with 6-12 carbon backbones have been used in various formulations. MCTs are metabolized more rapidly than long chain triglycerides in that they enter the body through the portal rather than lymphatic pathway. Metabolic products of MCT do not require carnitine to enter into the mitochondria where they undergo .beta.-oxidation.
One current high protein enteral liquid nutrition supplement, REPLETE.TM. (Clintec Nutrition Company), provides MCTs to minimize diarrhea caused by fat intolerance. Another formulation for enteral feedings, IMMUN-AID.TM. (Kendall McGaw Laboratories, Inc.), includes both MCTs and canola oil as sources of fat and is reported to improve immune function in an immunocompromised, stressed patient. Canola oil is discussed in the IMMUN-AID.TM. literature as being included in the composition as a source of .omega.3 fatty acids, which are reported to improve the cell-mediated immune response in animal models.
Canola oil not only provides .omega.-3 fatty acids; it and olive oil are the richest natural sources of monounsaturated fatty acids. Another new enteral product, PROMOTE.TM. (Ross Laboratories), uses high oleic acid safflower oil, canola oil and MCT's as lipid sources. The primary monounsaturated fatty acid in canola oil, olive oil, and high oleic acid safflower oil is oleic acid, an .omega.9 monounsaturated fatty acid. Monounsaturated oils are not appreciably elongated to a 20-carbon fatty acid. Thus, unlike oils high in polyunsaturated fatty acids, such as .omega.3 and .omega.6 fatty acids, administration of monounsaturated oils can not act as substrate in the prostanoid synthesis pathway which forms prostaglandins from fatty acids. Since the amount of certain prostaglandins in the system, particularly elevated levels of the "2" series prostaglandins, have been shown to be related to deleterious response to endotoxin in animal studies, reducing primarily with oils has positive health effects.
Accordingly, an object of the invention is to provide a method of treating patients having metabolic stress or sepsis using a diet which includes modifications in fatty acid content.
Another object of the invention is to provide an enteral or parenteral solution which can assist a patient combat challenge by metabolic stress or sepsis.
A further object of the invention is to provide an enteral or parenteral diet having reduced polyunsaturated fat content without the problems caused by high levels of MCT'S.
These and other objects and features of the invention will be apparent from the detailed description.